The cookie is read automatically in global.php
All you have to do is create your collapsible box correctly.
Replace what's in red
Code:
<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="180">
<thead>
<tr>
<td class="thead">
<a style="float:$stylevar[right]" href="#top" onclick="return toggle_collapse('MYBOX')"><img id="collapseimg_MYBOX" src="$stylevar[imgdir_button]/collapse_thead$vbcollapse[collapseimg_MYBOX].gif" alt="" border="0" /></a>
TITLE HERE
</td>
</tr>
</thead>
<tbody id="collapseobj_MYBOX" style="$vbcollapse[collapseobj_MYBOX]">
<tr>
<td class="alt1" nowrap="nowrap">CONTENTS HERE</td>
</tr>
</tbody>
</table>